• Journal of Korea Water Resources Association
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• v.55 no.12
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• pp.1021-1030
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• 2022

Currently, South Korea implements water resources management policies focusing on integrated water quantity, quality and hydro-ecology management. In particular, rehabilitation of natural rivers has become a major issue. As for reservoir operation during non-flood season, efforts have been made continuously to apply the Deficit Supply Method that can maximize water supply to address droughts and increase in water demand. When Deficit Supply Method is applied, the water supply capacity of reservoir can be maximized. However, downstream water flow would remain constant. In consideration that a natural stream, a long-time-created hydro-ecology, can be significantly influenced by flow variability, the Deficit Supply Method-based reservoir operation can generate effective water supply. Still, it may trigger adverse effects from the aspects of natural rehabilitation and hydro-ecology recovery. The main objective of this study is to analyze impacts on downstream flow duration through reservoir simulation by comparing the Firm Supply Method, the Deficit Supply Method and the Selective Deficit Supply Method, and examining each method's effects on reservoir operation. This study found that the Firm Supply Method could maintain water flow variability, but could not maximize water supply capacity. When the Deficit Supply Method was applied, water supply capacity could be increased while remaining vulnerable regarding water flow variability, as a difference between average flow and low flow was negligible at downstream. In comparison, the Selective Deficit Supply Method was found to sustain time-based reliability at 95% or higher, whereas downstream flow duration could be maintained at a level similar to the level generated by the Firm Supply Method.

• Journal of Korean Society on Water Environment
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• v.26 no.2
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• pp.208-214
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• 2010

This study aimed at the introduction of desktop method for assessment of environmental flows developed by International Water Management Institute (IWMI) recently and its application to Geum river basin. This scheme simulated the influence on aquatic ecosystem caused by watershed development and in turn the decrease of water quantity keeping the river's own flow regime. It was found to be as very effective method although it had simple structure. Flow duration curves for different environmental classes at Sutong and Gongjoo sites were estimated according to the natural conditional scenario of Geum river basin and the results were relatively compared well with the previous studies. The behaviors of monthly average runoff time series of both sites showed the level of A class. The results of this study would provide the fundamental data to establish the future plans of monitoring or management for aquatic ecosystem of Geum river basin.

• Journal of Korean Society on Water Environment
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• v.28 no.4
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• pp.574-581
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• 2012

It is important to analyze the status of water quality with relation to the stream flow to attain water quality goal more effectively in the unit watersheds for the management of Total Maximum Daily Loads (TMDLs). This study developed a flow duration-water quality distribution graph to figure out water quality appearances on the flow variation and analyzed contributions of water quality observations to the impaired water bodies quantitatively by hydrologic conditions. Factors relating to water quality variation can be analyzed more precisely and assessed on the base of quantified contributions. It is considered that this approach could be utilized to establish a more effective plan for the water quality improvement including the prioritization of pollution reduction options.

• Journal of Chest Surgery
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• v.22 no.2
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• pp.256-264
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• 1989

Modified Blalock-Taussig operation remains the standard technique of systemic-to-pulmonary artery shunt in patients of congenital heart disease with decreased pulmonary blood flow. We reviewed the 41 patients who had been performed modified Blalock-Taussig operation from March 1985 to Feb. 1988, and angiographically measured pulmonary artery size before and after shunt, and calculated pulmonary artery index [PAI] and ratio of left and right pulmonary artery to descending aorta[[LPA+RPA]/dAo]. The mean duration of palliation after shunt operation was 624 days and mean age of the patient at shunt operation was 3.59 years. Mean PAI increased significantly from 131.15*67.11 mm2/M2 preoperatively to 232.70*84.46 mm2/M2 postoperatively. Mean ratio of right and left pulmonary artery to descending aorta also increased significantly from 1.48*0.40 preoperatively to 1.92*0.50 postoperatively. All patients manifested clinical improvement; there was mean decrease in hematocrit of 8.95%, mean increase in arterial oxygen saturation of 11.08%. Pulmonary arterial growth was not influenced by age at operation, initial pulmonary artery size, or graft size, but significantly influenced by antegrade flow. The patients who have some antegrade flow were in more increase of PAI. There were no linear correlation between change of PAI, change of [[LPA+RPA]/dAo], SaO2, and duration. But, according to Scatterplot between change of PAI and duration, some complex correlation was suggested and mean PAI was decreased after 2-year palliation. We concluded that modified Blalock-Taussig operation is excellent palliative surgery for pulmonary artery growth especially on the patient who have some antegrade flow, and the proper duration of palliation was about 2 years.

• Journal of Korea Water Resources Association
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• v.54 no.6
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• pp.355-363
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• 2021

The conventional Flow Duration Curve has limitations that it does not consider hydrologic persistence of daily discharge, that the daily discharge is greatly affected by the maximums or minimums, and that the date of occurrence and duration of a specific discharge cannot be known. In this study, we propose a Daily Mode Discharge Curve, which consists of aligning the daily discharge each year by the date of occurrence, calculating the daily mode discharge, and averaging them every 5 days. As a result of reviewing the long-term observational daily discharge data at 8 points upstream and downstream of the mainstream of the 4 major rivers in Korea, it was found that the daily discharge at all points shows hydrological persistence, and the distortion of it was alleviated by using Daily Mode Discharge Curve. We also suggest that the Daily Mode Discharge Curve is useful for utilizing reference discharge such as Drought, Low, Normal, Plentiful, and Flood Discharge.

• Journal of Environmental Science International
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• v.17 no.11
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• pp.1295-1305
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• 2008

This study aims at the analyze of unsteady downstream flow due to dam failure along dam failure scenario and applied to Yeoncheon Dam which was collapsed August 1st 1999, using HEC-RAS simulation model. The boundary conditions of this unsteady flow simulation are that dam failure arrival time could be at 02:45 a.m. August 1st 1999 and failure duration time could be also 30 minutes. Downstream 19.5 km from dam site was simulated for unsteady flow analysis in terms of dam failure and non-failure cases. For the parameter calibration, observed data of Jeonkok station were used and roughness coefficient was applied to simulation model. The result of the peak discharge difference was 2,696 to $1,745\;m^3/sec$ along the downstream between dam failure and non-failure and also peak elevation of water level showed meanly 0.6m difference. Those results of these studies show that dam failure scenarios for the unknown failure time and duration were rational because most results were coincident with observed records. And also those results and procedure could suggest how and when dam failure occurs and downstream unsteady flow analyzes.

• Journal of Korean Society on Water Environment
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• v.29 no.6
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• pp.762-776
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• 2013

Load duration curve was applied to determine important water quality parameter control term for improvement of Paldang lake water quality. Load duration curve was analyzed with long term data from 1985 to 2012 including water quality, flow rate and climate state of Paldang water environment. From the result of flow rate patterns of paldang lake, differences between high and low flow rate of each year showed tendency of increase because rainfall characteristics of paldang lake watershed were changed by climate exchange. Both of land use state of upper Paldang lake watershed and number of limit excess from load duration curve indicated that seasonal action related with land use such as agricultural fertilizer distribution in upper watershed affected Paldang lake water quality. So focused BOD (biological oxygen demand) management during spring season from march to June is required to control organic materials in Paldand lake. The main affecting factor of TOC (total organic carbon) increase in Paldang lake was initial rainfall after march. T-N (total nitrogen) kept increasing during research period, so enhancement of T-N standard is needed to T-N control. Initial rainfall and increase of temperature during spring season from March to June showed a positive correlation with TP (total phosphorus) and Chl-a, respectively.

• Journal of Environmental Science International
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• v.28 no.10
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• pp.873-885
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• 2019

In this study, a load duration curve was applied to the Jangseongcheon, one of the tributaries of the Yeongsan River, to assess whether the target water quality was achieved. In addition, pollution of the water body was investigated to develop and suggest the optimal management time with respect to polluted flow sections and monthly conditions. The average flow rates of sections JS1 and JS2 were $0.25m^3/s$ and $1.08m^3/s$, respectively. The BOD and T-P for water-quality standards at JS1 were rated at II, whereas the COD and TOC were rated at III, thus indicating a fair level of water quality. By contrast, the BOD at JS2 was rated at III, the T-P at IV, and the TOC at V, indicating poor water quality in this section. The load duration curve was plotted using the actual flow data measured in eight-day intervals for eight years from 2011 to 2018 at locations JS1 and JS2 in the Jangsungcheon Basin. In an assessment using the load duration curve on whether the target water quality was met at location JS1, all of the water quality parameters (BOD, COD, TOC, T-N, T-P, and SS) satisfied the target water quality. By contrast, at location JS2, parameters COD, TOC, T-N, and T-P exceeded target values by more than 50%, indicating the target water quality was not met. The discharge loads of locations JS1 and JS2 were analyzed to identify the reasons the target water quality was exceeded. Results revealed that the land system contributed considerably. Furthermore, the discharge load of JS2 accounted for more than 80% of the load on the entire basin, excluding that of JS1. Therefore, the best method for restraining the inflow of pollutants into the stream near location JS2 must be applied to manage the water quality of the Jangsungcheon.

• Journal of Animal Science and Technology
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• v.48 no.4
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• pp.487-492
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• 2006

This study estimated characteristics and genetic parameters for milking traits in Holstein dairy cattle. Daily records (12,561) were available from a hundred fifty four lactating cows with sixty six sires at National Livestock Research Institute from November, 2005 to April, 2006. The cows were fed same rations, and were milked twice daily using milking parlour equipped with Alpro-system?? to collect milking records automatically. The experimental cows have averaged 1.9 parities, 139.7 days in milk, and 13kg milk yield per milking. Average milk flow was 64% of peak milk flow. Milking duration, peak milk flow, average milk flow, and milk yield per milking were 5.57±1.67 minutes, 3.58±0.79kg/minute, 2.28±0.51kg/minute, and 13.02±4.09kg, respectively. All traits in the morning milking were higher than those of in the evening milking, and were also increased with parity. Heritabilities for milking duration, peak and average milk flow, and milk yield per time were 0.49, 0.70 0.58 and 0.36, respectively. The genetic correlations of milking duration with peak milk flow, average milk flow, and milk yield per time were 0.48, 0.54, and 0.41, respectively. The correlations of milk yield per milking with peak milk flow and average milk flow were 0.23 and 0.30, respectively. In conclusion, milk flow was increased with milk yield; however milk flow was opposite relationship with milk duration. Further studies are not only necessary to warranty genetic parameters, but pre-installation of automatic recording system to collect daily milking record is also necessary.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.6
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• pp.123-133
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• 1995

An injection control valve(ICV) was designed to control the fuel flow between a common rail and an injector with two commercial solenoids. To improve the performance of ICV, the characteristic method was applied. With this method, the flow characteristics in the ICV and the injector were studied and the parameters which affect the injection characteristics were also studied. From this study, following results were obtained. The injection duration can be controlled and with modifications of the effective valve stroke of ICV, the injection quantity and duration can be reduced to desired amount. Also the injection quantity and pressure can be controlled by reducing the hole size of the injector without the variation of the injection duration. For some conditions, the desired injection characteristics can be obtained by the changes of the valve timing, the effective valve stroke, the open pressure of the injector and the hole size of the injector.